332 Fire-Clay Pockets at Clinton, la. — Farnsuorth. 
clay precisely like that found in the cavities before described, 
and of the character of under-clay, fills the upper and broader 
part of the cavity; while below this and occupying the deepest 
parts is a coarse sandstone which follows in its lines of lamina- 
tions the curvatures of the limestone upon which it lies. In 
the slaty portion have been found fish teeth of Carboniferous 
character." 
These descriptioDS would apply to cavities examined in the 
Niagara limestone at Clinton in almost every particular. Some 
facts must have escaped the first observers. In a quarry 
in the bluff near the river is a fine exposure of one of these 
cavities or fissures,extending for a distance of two hundred feet, 
and having a depth of from twenty to thirty feet and an 
irregular width of from five to ten feet. The top of the bluff 
was covered with four or five feet of loess or modified drift; 
then occurs what was once an opening not more than six feet 
in diameter, though it might have been longer. The cavity was 
filled to the depth of ten feet with a ferruginous sand, differing 
from the drift in color and composition; then a reddish arena- 
ceous clay; then the cavity broadened out in every direction into 
a long cave which was filled with laminated clay, conforming 
to all of the inequalities and sinuosities of the cavity . 
At a depth of ten or twelve feet from the opening appeared 
carbonaceous mud'similar to that spoken of as being found at 
Iowa City, these bands of carbonaceous clay or black lines in 
the clay extending down for a foot or more. In the lower 
levels of the cavern the clay completely filled the opening and 
no black bands appeared, but above that it was seen uniformly. 
No trace of fossils has been found in the clay, but in the car- 
bonaceous band pieces of pyritized wood and pieces resembling 
bark were taken out, resembling exogenous growth. The clay 
is of soft consistency and grayish color, burning nearly white, 
or the color of pottery clay. In fact a large portion of it was 
used in a pottery factory while some was used for fire-clay 
around the engines of the saw-mills. The carbonaceous band 
burns away leaving a trace of oxide of iron. The grayish clay 
yields no effervescence with acids and no trace of iron when 
heated. In other places are found similar cavities having no 
trace of the carbonaceous material, some of them containing a 
considerable amount of white sand. 
